1. Field of the Invention
This invention relates to a safety device used for an apparatus of the type having a frame, a stationary block fixed to the frame and a reciprocating member mounted on the frame, disposed above and in vertically opposed relation to the stationary block and adapted for forceful reciprocation thereto, such as presses, riveters, stakers, staplers and drills, which type of apparatus is hereinafter referred to as a "forceful reciprocation machine" for convenience's sake.
2. Prior Art
An example of safety devices of the type described is disclosed in U.S. Pat. No. 3,292,837 patented on Dec. 20, 1966. This safety device is shown as incorporated in a stapling machine for application of hook and eye fastener parts to fabric of a garment. The safety device broadly comprises a yoke or operating lever pivotally mounted on a frame of the machine, a safety guard or sensor pivotally mounted coaxially with the operating lever, and a switch provided above the common axis thereof and having a protruding plunger engageable with the rear end of the operating lever, and is systematically constructed that when the sensor has been fully lowered into engagement with the garment fabric and the operating lever has further turned over an angle of overtravel, the rear end of the operating lever is brought into impinging contact with the switch plunger, thereby activating a ram having a staple holder at its lower end.
Although, in general, having performed satisfactorily, this safety device has not been found to be entirely suitable in applications wherein the location for installment of the safety device is limited to a small space by a crowd of various components mounted on the complex forceful reciprocation machine and/or wherein extremely long serviceability of the safety device is a major requirement. Specifically speaking, the prior art safety device has encountered a drawback that, since the location to install the switch of the safety device is limited to a small area overlying the common axis of the operating lever and the sensor, the prior art safety device as a whole, in turn, sometimes finds a difficulty in being installed in such a complex machine having a large number of various components gathered closely together adjacent to the reciprocating staple holder. Further disadvantageously, the operating lever, at its rear end, is held into repeated impinging contact with the switch plunger, so that both operating lever and switch plunger are liable to be broken-down or made out of service in a relatively short period of time.